Selection and control of tolerance of thrust roller bearing chamber: the thrust roller bearing shall rotate flexibly without blocking sense after being pressed into the thrust roller bearing. If there is obvious inflexible rotation, it indicates that the size of the shaft is too large and the tolerance should be lowered. If the thrust roller bearing has obvious sense of 'sand' after being pressed into the shaft by hand, it may be that the tolerance of the shaft is too large or the roundness of the shaft is not good. Therefore, when controlling the tolerance of shaft and thrust roller bearing chamber, we should also control the roundness. Many domestic manufacturers only control the tolerance, but not the roundness.